A man hailing from Mumbai resembling the sketch of one of two suspects in the Samjhauta Express blasts was grilled in custody on Thursday as the Rajasthan police launched a hunt for another man whose wife was detained in Bikaner on Wednesday.

The Rajasthan and Haryana police were jointly interrogating the man from Mumbai resembling one of the suspects who had alighted from the train before the blasts and were looking for the husband of Sora, who was picked up on Wednesday night.

In all seven people have been detained so far in police raids in Rajasthan, Haryana, UP and Old Delhi, Haryana DGP Ranjiv Dalal told PTI.

Rajasthan Director General of Police A S Gill refused to reveal the identity of the detained man.

Five persons were detained in coordinated raids on Wednesday night by security forces in Kairana in western UP, Bikaner in Rajasthan and Old Delhi in connection with the train blasts.

Rajasthan Home Minister Ghulan Chand Kataria said the police had failed to elicit any "concrete clue" from the detained.

He said they are looking for Sora's husband.

Director of Forensic Laboratory, Haryana, J S Mahanwal said the pattern of the fire in the trans-border train shows that the bombers had used more than two suitcases, and it raised the possibility of five to six people involved in the attack.

"Since the suitcases are more than four, it is very well understood that one person cannot carry more than one suitcase because it must have weighed around 20 kg with the bottles and other material in it," he said.

"So, at least five to six people have been involved in placing these suitcases in the boggies," he added.

Meanwhile, police teams in UP, Delhi, Rajasthan and Haryana have questioned over 50 people as investigators said they were probing the case from "all possible angles."

"Interrogation in the case is on the right track," Dalal said in Panipat after a meeting with top district police officials.

He said investigations were at a preliminary stage and it would be premature to divulge any details.

"We have picked up a few people for questioning," Dalal said. Those picked up were being interrogated by Haryana police and central security agencies.

A senior Haryana police official said that they were also exploring the possibility of the bombers leaving the train at Delhi itself after planting the explosive device.